content: /**
   * Copyright (c) 2016-present, RxJava Contributors.
   *
   * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
   * compliance with the License. You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software distributed under the License is
   * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
   * the License for the specific language governing permissions and limitations under the License.
   */
  package io.reactivex.observable.internal.operators;
  
  import java.util.concurrent.Callable;
  
  import io.reactivex.common.*;
  import io.reactivex.common.functions.BiConsumer;
  import io.reactivex.common.internal.disposables.DisposableHelper;
  import io.reactivex.common.internal.functions.ObjectHelper;
  import io.reactivex.observable.*;
  import io.reactivex.observable.extensions.FuseToObservable;
  import io.reactivex.observable.internal.disposables.EmptyDisposable;
  
  public final class ObservableCollectSingle<T, U> extends Single<U> implements FuseToObservable<U> {
  
      final ObservableSource<T> source;
  
      final Callable<? extends U> initialSupplier;
      final BiConsumer<? super U, ? super T> collector;
  
      public ObservableCollectSingle(ObservableSource<T> source,
              Callable<? extends U> initialSupplier, BiConsumer<? super U, ? super T> collector) {
          this.source = source;
          this.initialSupplier = initialSupplier;
          this.collector = collector;
      }
  
      @Override
      protected void subscribeActual(SingleObserver<? super U> t) {
          U u;
          try {
              u = ObjectHelper.requireNonNull(initialSupplier.call(), "The initialSupplier returned a null value");
          } catch (Throwable e) {
              EmptyDisposable.error(e, t);
              return;
          }
  
          source.subscribe(new CollectObserver<T, U>(t, u, collector));
      }
  
      @Override
      public Observable<U> fuseToObservable() {
          return RxJavaObservablePlugins.onAssembly(new ObservableCollect<T, U>(source, initialSupplier, collector));
      }
  
      static final class CollectObserver<T, U> implements Observer<T>, Disposable {
          final SingleObserver<? super U> actual;
          final BiConsumer<? super U, ? super T> collector;
          final U u;
  
          Disposable s;
  
          boolean done;
  
          CollectObserver(SingleObserver<? super U> actual, U u, BiConsumer<? super U, ? super T> collector) {
              this.actual = actual;
              this.collector = collector;
              this.u = u;
          }
  
          @Override
          public void onSubscribe(Disposable s) {
              if (DisposableHelper.validate(this.s, s)) {
                  this.s = s;
                  actual.onSubscribe(this);
              }
          }
  
  
          @Override
          public void dispose() {
              s.dispose();
          }
  
          @Override
          public boolean isDisposed() {
              return s.isDisposed();
          }
  
  
          @Override
          public void onNext(T t) {
              if (done) {
                  return;
              }
              try {
                  collector.accept(u, t);
              } catch (Throwable e) {
                  s.dispose();
                  onError(e);
              }
          }
  
          @Override
          public void onError(Throwable t) {
              if (done) {
                  RxJavaCommonPlugins.onError(t);
                  return;
              }
              done = true;
              actual.onError(t);
          }
  
          @Override
          public void onComplete() {
              if (done) {
                  return;
              }
              done = true;
              actual.onSuccess(u);
          }
      }
  }
  